Electrolytic cell tank construction



Dec. 10, 1 D. M. BUCHANAN ELECTROLYTIC CELL TANK CONSTRUCTION Filed Sept. 25," 1954 INVENTOR DAVID M.-BUCHANAN M 530% V NEY llllllii nited States Patent- ELECTROLYTIC CELL TANK CONSTRUCTION David M. Buchanan, Woodside, N. Y., assignor to Union Carbide Corporation, a corporation of New York Application September 23, 1954, Serial No. 457,934

1 Claim. (Cl. 204279) The present invention relates to an improved cell tank for use in the electrowinning of metal values from an electrolytic solution.

Conventional electrolytic cell tanks are constructed primarily of wood. A metal lining, usually lead, is provided on the inside of the tank to prevent chemical reaction between the wood and the electrolytic solution.

A disadvantage arising from the use of such a construction is the fact that most electrolytes react to some extent with the lead lining and cause corrosion of the lining. This creates leakage problems, weakens the cell tank lining and eventually causes warpage of the wooden structural members.

Attempts were made in the past to solve this problem by using as cell tank materials, compounds having chemi cal resistance to electrolytic solutions such as resinous organic compounds. But up to now this has not been practical primarily because the materials which were heretofore considered were lacking in structural strength and rigidity. Strength and rigidity are requisite structural features for a cell tank since the tank must be capable of sustaining the weight of thousands of gallons of electrolyte as well a auxiliary tank equipment. If cell tanks could be inexpensively made from organic compounds that are non-reactive with most electrolytes and could be suitably formed to withstand the stresses and strains imposed upon it by the auxiliary equipment and materials associated with it, it would open a field of application that is not as readily available to conventional cell tanks currently being used.

It is, therefore, an object of the present invention to provide a cell tank having good strength and toughness qualities at the temperatures normally encountered in electrolytic processes, and having high resistance to chemical attack by solutions used in the electrowinning of metals and other electrolytic processes.

Another object of the invention is to provide a cell tank that can be made by molding in one piece, or easily assembled with a small number of parts from an organic material having high dielectric properties and chemical resistance to electrolytic solutions used for the electrowinning of metals or other electrolytic processes.

In the drawings:

Fig. 1 is a perspective view of a cell tank constructed in accordance with the principles of the present invention;

Fig. 2 is a sectional elevation-a1 view of the cell tank shown in Fig. 1;

Fig. 3 is a sectional view of the cell tank shown in Fig. 2, taken along the line 33; and

Fig. 4 is an enlarged sectional view of the encircled area 4 in Fig. 2, showing important details of the reinforced cell tank lip of the present invention.

The present invention is an improvement upon prior art cell tank materials. It has been found that a very suitable cell tank to be used in electrolytic processes can be produced from contact resins such as laminating resins comprising unsaturated esters which can be polymerized either alone or in admixture with other un- 2,816,970 Patented Dec. 10, 1957 saturated monomeric substances, to yield thermohardened, cross-linked polymers. The fundamental requisite of these esters is the presence of at least two polymerizable double bonds in their unit structure.

There are two general categories of such esters available at present. The first type comprises unsaturated linear polyesters produced from a glycol and maleic acid, or some other unsaturated dicarboxylic acid as, for example, C-arblc" anhydride. Such polyesters may be modified with unsaturated alcohols like allyl alcohol. The presence of double bonds in the polyester chain permits subsequent copolymerization with other added monomeric unsaturates such as styrene. Because of the polymeric character of the ester, these resins are moderately viscous before polymerization, a fact which has been found to facilitate mechanical handling during impregnation. I The second type of laminating resin consists of doubly unsaturated monomeric esters. Important commercial representatives of this group include monomolecular esters of allyl alcohol and dibasic acids or their derivatives which still contain two esterifiable carboxyl groups.

Obvious modifications of this second group include monomeric esters of unsaturated alcohols and unsaturated monoor dibasic acids, such as allyl itaconate and glycol or polyglycol esters of unsaturated acids, such as methacrylic acid. These monomeric liquids are nonviscous, because of their low molecular weight, and must be used with care in laminating operations in order to avoid resin segregation in shaped sections.

The preferred compound within practice of the present invention is an unsaturated polyester combined with styrene such as disclosed in the U. S. Patent No. 2,475,731 to G. S. Weith, issued July 12, 1949. This polyester resin is made. by reacting polyester with an alphasubstituted ethylene compound such as styrene, viny acetate, acrylic acid, and methacrylic acid.

In cell tanks of the present invention, polyester resins may be used without reinforcing material. However, the advantage of strength, toughness and stability are more 'fully realized when they are combined with reinforcing material. Preferably, the reinforcing materials are based on glass and are used in the form of fabric.

The advantages of the present invention are quite substantial. At the temperatures encountered in normal electrolytic processes, cell tanks made of polyester resins of the type described hereinabove exhibit advantages'of strength, light stability, alkali resistance and water resistance, particularly with higher ratios of styrene included therein. Further, cell tanks embodying the principles of the present invention can be conveniently made into final form by conventional production methods such 'as diaphragm molding or rubber plug molding or matched metal molding or vacuum forming. The cell tank also has the advantage of simplified construction in that it may be made in one piece or from a small number of parts. Another advantage arising from the use of the present invention is the fact that it has a light weight in comparison to metal or wooden structures, and exhibits relatively high structural strength, excellent impact shock resistance and chemical inertness to most electrolytesat temperatures up to about 200 F.

The cell tank of the present invention is particularly well suited for use in the electrowinning of metals such as chromium and manganese, which deposit out of aque: ous electrolytic solutions. Moreover, the cell tank of the present invention is not affected by electrolytes hav ing a chloride or sulfate radical, and is resistant to chemi 3 with-glassofthe type-described hereinabove. This cell tank may comprise an elongated box-like structure having a pair of spaced side walls, 12, 13, end Walls 14, 15 and a bottom 16; the cell'compartment being=suitably fabricated as by injectionrnoldingorimpregnation of afabric-ba'se. According. to 'the present invention, the polyester resin material of the cell container maybe fabricated preferably in one'piece, although-prefabricated cellwalls or portions thereofmay be suitably secured-to each other cor'din'gly, the sidewalls 12 and 130f the cell tank are provided-with integralstrengthening ribs 18 and 18a, *which are arranged in vertical and parallel manner. The

lower ends of each of the ribs 18 and 18a are respectively united by parallel'ribs 18b,-which are integral with the bottom wall 16. -Vertical'and spaced'ribs 18c'and 18a in the end walls '14 and 15, respectively, merge with the 'cndmost ribs 18b. The rib cross sections may be-of any shape, a T-shaped rib 'being preferred and illustrated herein.

The vertical ribs, 18,18a, 18c, and 18d, of'the cell 'tanks'terminate in a lip '19which is molded around a steel reinforcement for strengthening purposes. This reinforcement comprises a channelled beam 20 of U cross section (see Fig. 4) having a central web 21 and a pair of end flanges 22. A steel plate 23 welded to the outside of each flange 22 lends further strength to the structure. The bight of the channel beam 20 is provided with a filler material 24 made of wood or the equivalent to prevent the formation of voids during molding.

Anolyte and catholyte solution may be introduced into the cell tank 10 by means of openings 25 and 26, respectively, in the. cell cover 30. The anolyte-and catholyte liquids traversethe passages between the cell units of the container 10, andare carried outwardly through overflow discharge openings27 and 28, which maintain the level 'of the respective liquids in tank 10 at predetermined and fixed levels. Drainage of the cell tank may be accomplished by providing an opening 29 in the end wall 24 adjacent the bottom thereof, and pitching the bottom wall 16 toward said opening.

-A number of covers are employed to enclosethe cell units in the tank-10 for the purpose of removing fumes and venting the electrolysis apparatus when necessary. Four covers, 30, 31, 32, and 33, are illustrated in the drawing but a smaller or larger number maybe used. These covers may be formed of a material similar tothat of the cell tank. The covers are carried by ahinge leaf 34, which is pivotally secured to a hinge strip 35. attached to the top of the cell tank 10. 'The covers 30, 31,?32, and 33 are held in place by hold down bolts 36 (see Fig. 4) passing through bolt apertures 37 in each of the covers and registering threaded bolt apertures 38 in the .cell tank lip 19. A tapered vent opening 39 in.the cover serves to remove gases and air from the confines otthe cell tank. If desired, the covers may be dispensed withori rotated upwardly and the top of the tank left open. Open topped containers oifer convenience in removing .electrodes,..attaching liquid lines and in visually inspecting the cells during. operation.

Success of the tank embodied in the patent'invention hinges on critical proportions and dimensions. For example, for a cell tank having a capacity of. 1,200 gallons of electrolytic solution and capable of sustaining; a load of 15,000 lbs., the following dimensions are recommended.

- The tank-"should have a length of approximately -10 feet,

width of 3 feet, and a height of 4 feet. Wall thickness may vary from M4 to an all-round wall thickness of being preferred. Ribs should be spaced not more than 15 inches apart and preferably less than 13 inches apart.

Because the material used in the fabrication of the cell of the instant invention is lighter and less expensive, it effect-s savings in material and does not pose problems which require special'handling in the installation'thereof. The polyester resin tank material combines resistance to chemical attack with high strength physical properties, and obviates the need for separate structural members and protective liningmaterial therefor.

Cell tanks embodying the principles of the present invention may be molded or fabricated in one piece, or in parts that may be cut loose from a strip of the tank material. -Handling and construction may be facilitated by assembling the tank'parts-at the plant location. 'Au'tomatic control equipment and improvedmolding and fabrication techniqueshave made this operation practical in routine production. In addition, the improved celltank presents "a sturdy "monolithic structure which is" light weight, lea'kproof, corrosion resistant and susceptible of being produced in "accordance with the present day*production methods. Moreover, the instant cell tank is ad- 'mirably suited for-use in the production of electrolytic chromium, manganeseyor other similar metals,-where chemi'calreaction between the electrolyte and the tank wall is a problem.

What is claimed is:

A rectangularnon-conductive electrolytic cell tank of unsaturated polyester combined with styrene of the type used in the'electrowinning of metals, said cell tank comprising 'an'elongated rectangular bottom wall,-a pair of spaced rectangular side walls and a pair of spaced'rectangular end'walls, said walls being integrally united'to form a self-supporting electrolyte-receiving region'of rigid construction and high cubic capacity, means for introduc- 'ing' anolyte and catholyte solutions'into' said region, a pair ofdiseharge openings'in one of said' end walls for respectively removing spent catholyte and anolyte solutionsfrom 'said' cell'tank and simultaneously maintaining said 'solutionsv in said'region at predetermined and fixed levels, a continuous 'metalreinforced lipintegral'with the tops'of said side and end walls, and a" plurality ofclosely'spaced, parallel, vertically extending, longitudinally spaced, T- shaped' ribs integrally disposed on the outer sidesof said sidewalls, the"ribs' on'one of said side walls being in registrywith the ribson the'other side wall, a plurality of longitudinally spacedribs on saidbottom wall, each of said bottom wall ribs" having its ends .integrallyunited with a pair ofregi'stering sideribs, and a plurality of transversely .spaced, vertically extending ribs integrally disposed on the outer. sides. of the end walls having in- Iegrakextensi'ons extending along and longitudinally'of said bottom wall terminating at and integrally joined to the'b'ottom ribs adjacent therespective end wall. from which eache'xtends, said ribs being effective inimparting strength and rigidity to. said cell tank and said rib reinforcedwalls being effective. in sustaining the weight of said container'and' its contents.

References Cited in the file of this patent UNITED. STATES PATENTS 1,271,690 .Ford July 9, 1918 1,829,935 :Klock Nov. 3 1931 2,475,731 'Weith July '12, 1949 

